Computer pointing devices include movable computer mouses commonly used with a portable computers and stationary trackball devices commonly used with laptop computers. A trackball is employed in a computer pointing device to engage direction sensors which register directional movement of the trackball. The computer pointing device communicates the registered directional movement to a cursor associated with a computer screen.
During movement, trackballs collect dirt, dirt marks, skin particles and other matter from mouse pads, other underlying surfaces on which computer pointing devices rest, the fingers of the user and other items which contact trackballs. The dirt is eventually transferred from the trackball onto the direction sensors of the computer pointing device. Indeed, conventional trackballs effectively transfer dirt to direction sensors under the same principle that a ball in a ballpoint pen transfers ink to paper.
The direction sensors which are loaded with dirt no longer respond in the intended manner. Depending on the nature of the dirt (e.g., old dirt hardens if it is not removed) and on the design of the sensor, the control signals to the computer may become incorrect.
In conventional circumstances, the user is unaware of the fact that dirt is affecting the pointing device in an adverse manner and contacts service personnel to request correction of a badly functioning computer. Consequently, the user incurs an unnecessary expense which would not occur had the user been aware of the actual cause of the problem.
On the other hand, if the user is aware of the problem with dirt fastening on the computer pointing device, he can, for example, shake the mouse or rub the mouse over an underlying surface in an attempt to loosen the dirt. If this activity does not solve the problem, the dirt must be removed by hand. Thus, in the case of a computer mouse, the user must remove the plate which holds the trackball in place and shake the mouse to loosen the trackball out of the mouse. Correspondingly, in the case of a stationary trackball employed in a laptop computer, the user must remove a locking plate, turn the computer upside down and shake the trackball loose. The user cleans the plate and the trackball by blowing away the dirt or by removing the dirt with a rag or a cotton pad, possibly with the aid of a suitable cleaning solution. In order to clean the direction sensors, the user can use his nails, other thin devices or a cotton pad to remove the dirt. The direction sensors are more inaccessibly placed inside the computer pointing device. Since the direction sensors are often fixed so as to easily rotate around an axis, these sensors tend to rotate as soon as they are touched, making cleaning difficult. The actual cleaning, therefore, may take an appreciable amount of time (e.g., 15-20 minutes is not unusual).
U.S. Pat. No. 4,673,440 to Chapin, Jr. and published British Patent Application GB-A-2,268,049 to Burton teach apparatuses for cleaning trackballs. U.S. Pat. No. 4,673,440 discloses a cleaning ball covered with a VELCRO material which is used together with an underlying surface, also of a VELCRO material, to clean a computer mouse. British Patent Application GB-A-2 268 049 discloses a ball fitted with a stick for cleaning direction sensors in a computer mouse. However, these patents do not disclose a trackball which can temporarily or permanently replace the existing trackball in a computer pointing device to clean the direction sensors.